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John
Spence

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The Spence group undertakes experiments in biophysics, condensed matter, and diffraction physics based around the use of electron and X-ray laser beams for imaging, spectroscopy and diffraction. John is Director of Science for the NSF's Science and Technology Center for application of X-ray lasers to structural biology, a seven-campus consortium funded from October 2013 (http://www.bioxfel.org). This supports the research of six faculty at ASU. Along with Profs U. Weierstall and R. Kirian, John supports the STC program with research in the area of diffraction physics, algorithm development and XFEL hydrated sample delivery. (Other STC researchers at ASU support work on photosynthesis, nanocrystal growth and single-virus diffraction). We work closely with staff scientists at the world's first hard-Xray laser, the DOE's LCLS at SLAC. We use femtosecond X-ray pulses containing about 1E12 photons so brief that they terminate before atoms move (in order to avoid radiation damage), to determine the structure of membrane proteins and viruses which are difficult to crystallize. Projects are also based on the facilities of the Cowley electron microscope center, together with new instruments we have built or modified ourselves, such as, our Scanning Atom Probe, which integrates a time-of-flight spectrometer with an STM, and a new low-temperature STM. Our quantitative convergent beam (QCBED) research allowed us to directly image the chemical bonds which bind atoms together in solids. This experimental work is accompanied by band-structure calculations, which allow us to test the latest many-electron approximations used against experiments. Theoretical work continues on the inversion problem of multiple scattering, and experimental research is supported on the use of coherent sub-nanometer electron probes for the study of dislocation core structures, and on electron channelling effects on X-ray production (ALCHEMI). We are also involved at Lawrence Berkeley Laboratory in research into lensless X-ray imaging methods. John is the recipient of the Buerger Medal of the ACA, the Cowley Prize of IFSEM, Distinguished Scientist medal of MSA, and is a Fellow of AAAS, APS, MSA, IOP and Churchill College Cambridge. He is currently Main Editor for IUCRJ (XFEL Science).